Quarterly estimated taxes: 2026 deadlines and how much to pay

The word "quarterly" is doing a lot of false advertising here. Most self-employed clients assume the year splits into four even three-month blocks. It doesn't, and the uneven split is exactly the kind of thing that causes someone to underpay the third one without realizing it.

Who this applies to

If you're self-employed, work as a 1099 contractor, run a small business, or have meaningful income that isn't covered by paycheck withholding, and you expect to owe $1,000 or more for the year, the IRS wants that money paid roughly as you earn it rather than all at once in April. This is the group we deal with constantly at Tax Shop: Schedule C sole proprietors and small S-corps in the Lone Tree and Denver metro area who went from a W-2 with automatic withholding to income nobody's withholding anything from.

The 2026 due dates

April 15, June 15, and September 15, 2026, then January 15, 2027 for the fourth and final payment of the year. If any of those lands on a weekend or federal holiday, it pushes to the next business day.

Here's the part that trips people up: those aren't four equal quarters. The first period runs January through March, three months. The second covers April and May only, two months. The third runs June through August, three months. The fourth stretches from September through December, four months. Whoever designed this wasn't thinking about round numbers, so don't assume each payment covers the same amount of income.

How much keeps you out of penalty territory

The IRS gives you a safe harbor, and hitting it means no penalty regardless of what you actually end up owing. Pay the smaller of two numbers: 90 percent of what you'll actually owe for 2026, or 100 percent of your total tax from 2025. If your 2025 adjusted gross income was over $150,000 (or $75,000 if you're married filing separately), that second number becomes 110 percent instead of 100.

Most people find the prior-year number easier to hit, since it's already known rather than estimated. Say your total tax last year came to $12,000: four payments of $3,000 each puts you in the safe harbor no matter how this year turns out. If last year was unusually high or low for you, running the current-year 90 percent option might save you real money instead.

How the penalty actually works

It's not a flat fine. The IRS calculates it period by period, tied to the federal short-term interest rate, and it compounds the longer the shortfall sits unpaid. A big payment in January doesn't retroactively fix an April or June shortfall; the penalty clock for that period already ran. That's the detail people miss when they try to catch up all at once at year end.

Where to send the money

IRS Direct Pay is the easiest option: free, no account required, pulls straight from your bank account. EFTPS works too if you want the payment history in one place. Mailing a check with the Form 1040-ES voucher still works, it just takes longer and gives you a paper trail instead of an instant confirmation number.

Colorado runs its own estimated payment system for state tax on a similar quarterly schedule, separate from the federal payments. If you're paying federal estimates, budget for the state ones too. And since estimates are calculated on your profit after deductions, it's worth knowing what a small business can actually write off before you settle on a number.

Common questions

General information from Tax Shop in Lone Tree, Colorado, current as of August 20, 2026. Tax rules change and every return is different, so this is not advice about your own situation. Ask us about your return.